Engineering topics

Steele, L. P.

Publications and source records attributed to Steele, L. P..

3 records

NASA NTRS1992

Carbon monoxide and methane in the North American Arctic and Subarctic troposphere - July-August 1988

Enhanced concentrations of CH4 in the unpolluted atmospheric mixed layer over both Arctic and subarctic tundra landscapes are documented here using data from the NASA Arctic Boundary Layer Expedition (ABLE 3A). The CH4 concentration gradients were determined mainly by interactions of biogenic emission from wet tundra and turbulent mixing proceses. The gradient were most frequently associated with intrusion of upper tropospheric or stratospheric air into the midtroposphere, emissions from forest and tundra fires, and long-range transport of enhanced concentration of these gases from unidentified sources. Summertime haze layers exhibited midtropospheric enhancements of CH4 similar to those measured in winter Arctic events. The observations confirm the importance of Arctic and Subarctic wetland environments as a regional source of global atmospheric CH4.

Harriss, Robert C.↗

NASA NTRS1989

Trends in source gases

Source gases are defined as those gases that, by their breakdown, introduce into the stratosphere halogen, hydrogen, and nitrogen compounds that are important in stratospheric ozone destruction. Given here is an update of the existing concentration time series for chlorocarbons, nitrous oxide, and methane. Also reviewed is information on halogen containing species and the use of these data for establishing trends. Also reviewed is evidence on trends in trace gases that influence tropospheric chemistry and thus the tropospheric lifetimes of source gases, such as carbon dioxide, carbon monoxide, or nitrogen oxides. Much of the information is given in tabular form.

Ehhalt, D. H.↗

NASA NTRS1984

Tropospheric methane in the mid-latitudes of the Southern Hemisphere

More than 800 methane concentration measurements have been obtained for the Southern Hemisphere's troposphere over the September 1980-March 1983 period. Concentrations are noted to increase throughout the troposphere during the study period, adding further support to the view that CH4 concentrations are currently increasing on a global scale. In the surface methane data, a seasonal cycle with a peak-to-peak amplitude of 28 ppbv is found. Maxima and minima are on September-October and March, respectively. The phase and amplitude of the cycle are qualitatively consistent with the concept that the major sink for methane is oxidation by hydroxyl radicals. Evidence is found for a positive vertical gradient in methane content.

Fraser, P. J.↗